RPM reading problems

For discussing how to choose sensors and create a wiring harness for all Bowling and Grippo versions of the MegaSquirt® EFI controller.
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r1go
MegaSquirt Newbie
Posts: 9
Joined: Sun Jun 15, 2014 7:08 am

RPM reading problems

Post by r1go »

Hi everyone!

My project: BMW e21 320i /6 with Megasquirt v2.2
I cant figure it out where do i have to connect the rpm wire signal for the dash from the MS.
If i read the value from th MS with a pc/cellphone (bluetooth) values are OK, but in the dashboard looks like the "real" value is divide by 3.
When the car is idling, i get 1000RPM which is correct for me, but if i press gas, i cant get higer values than 3000RPM.

At the moment theres only one wire from the DB37 #34 connected directly to the dashboard
What im doing wrong? The MS works with a different kind of signal and the BMW dashboard does not understand it well?

Thankx in advance! I hope to get this working soon :)
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Matt Cramer
Super Squirter
Posts: 2951
Joined: Sat Jul 03, 2004 11:35 am

Re: RPM reading problems

Post by Matt Cramer »

Pin 34 is an injector output. Why is it wired to the tach?
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r1go
MegaSquirt Newbie
Posts: 9
Joined: Sun Jun 15, 2014 7:08 am

Re: RPM reading problems

Post by r1go »

I have no idea because, I didnt do it.
The mecanic told me that maybe the RPM its broken. Today im gonna test it and try with another one.
but besides that, where it should go?
I have 3 doble coil ignition with spark missed ignition by the way.
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Matt Cramer
Super Squirter
Posts: 2951
Joined: Sat Jul 03, 2004 11:35 am

Re: RPM reading problems

Post by Matt Cramer »

The RPM is "broken" because you are using something that was never intended to be an RPM output for that purpose.
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trakkies
Super Squirter
Posts: 1162
Joined: Tue Dec 30, 2008 3:06 am
Location: SW London, UK

Re: RPM reading problems

Post by trakkies »

r1go wrote:I have no idea because, I didnt do it.
The mecanic told me that maybe the RPM its broken. Today im gonna test it and try with another one.
but besides that, where it should go?
I have 3 doble coil ignition with spark missed ignition by the way.
How did the rev-counter originally get its tach signal? I'd guess being an older car, it was fed direct from the single coil negative. In which case it expects to see a pulse of some 50 volts or so.
MS on its own can't generate that sort of pulse.
So if you've converted to wasted spark, you need to use one of the methods given in the manual to derive a suitable pulse to drive your rev counter. Or buy an adaptor from an MS supplier.
Dave P, London UK.
Rover V-8
MSII V3
EDIS
Tech Edge Wideband
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r1go
MegaSquirt Newbie
Posts: 9
Joined: Sun Jun 15, 2014 7:08 am

Re: RPM reading problems

Post by r1go »

That was exactly the answer that i was waiting for.
I thought something like that.

Can you tell me exactly which adapter should I get?

Thanks so much, that was very helpful
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trakkies
Super Squirter
Posts: 1162
Joined: Tue Dec 30, 2008 3:06 am
Location: SW London, UK

Re: RPM reading problems

Post by trakkies »

I made my own, so haven't any direct experience of the commercial ones. And I don't even know what country you live in. Best to contact your MS dealer and explain you're using wasted spark and need an adaptor for an old style rev-counter.
Dave P, London UK.
Rover V-8
MSII V3
EDIS
Tech Edge Wideband
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r1go
MegaSquirt Newbie
Posts: 9
Joined: Sun Jun 15, 2014 7:08 am

Re: RPM reading problems

Post by r1go »

Great! Can you explain me how to do it?
I live in Montevideo, Uruguay and there's no local dealership of pretty much nothing :/.
I would be very appreciate if you led me throughout this.
I always try to solve this sort of problems by my self.

Thanks in advanced!!
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trakkies
Super Squirter
Posts: 1162
Joined: Tue Dec 30, 2008 3:06 am
Location: SW London, UK

Re: RPM reading problems

Post by trakkies »

You'll find details in the manual under Ford EDIS. It's only a few diodes which combine the pulses from all of your coils.

Or you can build a simple circuit which generates a high voltage pulse. I think you'll have to go to the Extra site to find details - look at pages 41 and 42 of the MS2V3 manual.
Dave P, London UK.
Rover V-8
MSII V3
EDIS
Tech Edge Wideband
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r1go
MegaSquirt Newbie
Posts: 9
Joined: Sun Jun 15, 2014 7:08 am

Re: RPM reading problems

Post by r1go »

Thanks a lot!
Hands to work!
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r1go
MegaSquirt Newbie
Posts: 9
Joined: Sun Jun 15, 2014 7:08 am

Re: RPM reading problems

Post by r1go »

Hey there!
Sorry for waiting so long for the pictures!
Here is the link to my dropbox account, i've just put lots of picture from my MS v3.0 (i thought it was a v2.2 ).
Maybe you cand tell me whats wrong with it and why it is sending a wrong signal.

https://www.dropbox.com/sh/h8tr5uyq2qk4 ... L4bQa?dl=0


Thanks a lot for this help, i really appreciated!!!!
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